1. Field of the Invention
Embodiments of the invention relates in general to improving the performance of petroleum-bearing formations and, in particular, to an improved system, method, and apparatus for distributing nanocatalysts in petroleum-bearing formations.
2. Description of the Related Art
Vast quantities of heavy oil and bitumen are found in Canada, Venezuela, and the United States. These resources of heavy oil and bitumen are typically characterized by having low specific gravities (0-18° API), high viscosities (>100,000 cp), and high sulfur content (e.g., >5% by weight). As a result, these resources are difficult and expensive to refine into saleable products.
Pyrolysis occurs when oil thermally cracks at temperatures greater than about 650° F. Although pyrolysis reduces the viscosity of oil, sometimes dramatically, it often results in the formation of large quantities of coke. This thermal reaction also causes a desirable increase in the API gravity, but it has little effect on the sulfur and tends to raise the total acid number, which sharply reduces the value of the oil to refiners. To overcome these limitations, it would be helpful to have an in situ process for upgrading the raw material before it is produced from the wells.
Conventional, aftermarket refining provides two alternative types of refining processes for the initial upgrading step: (1) carbon removal (e.g., delayed coking), or (2) hydrogen addition (e.g., hydrogenation). Delayed coking is not well-suited for in situ upgrading because of the high temperatures (e.g., about 900° F.-1,250° F.) and the short reaction times (e.g., about 2-3 hours) required to complete the process.
With regard to hydrogenation, nanocatalysts have been developed for various chemical reactions used in refining applications. Nanocatalysts are beneficial for upgrading, and include alkylation of aromatics over TiO2, isomerization of alkanes over TiO2, dehydrogenation/hydrogenation of C—H bonds over TiO2/Pt, hydrogenation of double bonds over TiO2/Ni, and hydro-desulfurization of thiophene over TiO2/Ni/Mo. However, the stumbling block that prevents the application of these solutions to in situ upgrading is the lack of technique or method to inject the appropriate catalysts (e.g., nanoparticles) and then disperse them throughout a portion of the target reservoir.
Processes for the in situ conversion and recovery of heavy crude oils and natural bitumens from subsurface formations have been described. A mixture of reducing gases, oxidizing gases, and steam are fed to downhole combustion devices located in the injection boreholes. Alternatively, the gas mixture may be provided from the surface. Combustion of the reducing gas-oxidizing gas mixture is carried out to produce high quality wet steam or superheated steam and hot reducing gases for injection into the formation to convert and upgrade the heavy crude or bitumen into lighter hydrocarbons. The excess reducing gas that is not used as fuel is injected into the formation for converting oil in place to less viscous oil and upgrading the tar. Although this solution is beneficial for many applications, it is not suitable for introducing and distributing nanocatalysts in an oil-bearing formation.